The present invention relates to client-server networks and, in particular, to methods and apparatus for remotely executing an application and displaying application output.
Contemporary computer networks consist of a number of computer systems, called nodes, communicating with other computer systems via communication links. Typically, some of the nodes are client nodes and other nodes are server nodes. A client node formulates and delivers queries to a server node. A user of the client node enters the queries through a user interface operating on the client node. The server node evaluates the queries and delivers responses to the client node for display on the client user interface.
Usually, the server nodes host a variety of application programs or processes that can be accessed and executed by client nodes. When a client node launches an application program, the execution of that application program can occur at either the client node or the server node, depending upon the computing model followed by the computer network.
In a client-based computing model, the application program is packaged and sent down to, or pre-installed on, the client node, allowing the client node to run the application using the resources of the client node. This approach has several drawbacks. First, the client node must have sufficient memory, disk space, and processing power to effectively execute the application. A related problem that occurs using this model is that the number of applications a given client is able to execute is limited due to client resource constraints. Further, applications built this way are complex to develop and maintain and typically require modification or xe2x80x9cportingxe2x80x9d for all supported client computer system types. Moreover, this technique exacerbates the administration burden on a network administrator.
In a server-based computing model, the server node executes the application program, and only the control information for the client user interface is transmitted across the computer network to the client node for display. Using this approach, user interface events must be sent between the client and the server in order for the server application to process the events. This results in perceived delays of user interface response. Further, the application program must be specifically written, or changed, to support the user interface on the client node. This increases the complexity of the application and prevents this technique from being useful with off-the-shelf applications.
A refinement of the server-based model is to supplant the device driver to which the application communicates in order to send screen and device updates back and forth between the client and the server. This approach avoids requiring applications to be rewritten. However, this approach requires device information to be sent between the client and the server in order to maintain the client display, again introducing perceived latency into the interface. Further, server-side processing requirements are increased in order to satisfy resulting device information required for communication with each connected client.
A recent, further refinement of the server-based model is to deploy the user interface portion of the application as a mark-up language document such as Hyper Text Markup Language (HTML) document. However in using this approach, information sent from the server application to the client begins to xe2x80x9cagexe2x80x9d immediately. In other words the information may change on the server but the client would not automatically be notified and updated. Further, with this approach interactivity requires context switching between pages even to perform simple tasks.
The present invention avoids these shortcomings.
The present invention provides a mechanism by which the user interface portion of the application can be delivered to the computer user either on the same machine on which the application is executing or on another machine remote from the machine executing the application. The invention separates the user interface from the underlying application enabling the user interactive portion of the application to be extremely simple. The invention also permits the user interactive portion to be deployed on a wide range of client hardware environments without bringing with it all the required logic for performing the functionality of a particular application. These features give the user the effect of directly interacting with whole application even though the main part of the application is potentially running somewhere else.
Thus, the present invention overcomes many of the problems faced by traditional approaches outlined above. User interface, event handling and screen rendering logic stay on the client, thus dramatically reducing network traffic and latency. The entire user interface and how that interface connects to application components on the server are sent as a pure data description to the client (rather than code). This description is xe2x80x9cinterpretedxe2x80x9d by the client to render the graphics user interface (GUI) and connect to the application (through the transfer of state) running either in the same process space (same machine) or on the server (remote machine).
Because the server can communicate with a particular application client with simply a data description, no additional code needs to be installed on the client machine. An application-independent client process (AICP) reads the description and presents that description to the user as a typical client user interface. Therefore, the AICP can communicate with an unlimited number of server applications with a new data file description for each program (which can be cached automatically as required or as specified by the client). No application specific administration is required for executing an AICP-deployed application using this approach.
With the AICP, no server side processing is required to either render the user interface portion or handle the GUI events portion of the application. The server does, however, coordinate state information being passed to and from the client and sends that information automatically to the appropriate application components involved (both client and server initiated data changes).
Using the AICP, the developer can focus primarily on the functional or business logic portion of the application and let the AICP handle all of the user interface rendering, event handling, and connection of the user interface controls with the underlying application components. A builder component allows the developer to layout the user interface windows as well as create a relationship between the visual control and the underlying application server component with which it is associated. With the AICP no application specific code needs to be sent to the client. Only user interface controls need be sent if required. Even though there is no code on the client, the user""s experience with the client application is similar to hand-coded clients found in the client based mode. In one embodiment the AICP is embedded in an HTML browser environment which enables web deployment within an HTML page without the limitation associated with HTML.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of the embodiments of the invention, as illustrated in the accompanying drawings.